(1) Field of the Invention
This invention relates to the use of high transmittance dark tone attenuating phase shifting masks to form contact holes in a layer of negative resist wherein the contact holes have a width and separation in the 0.1 or above micrometer range.
(2) Description of the Related Art
The use of attenuating phase shifting material in photolithography is frequently used in the fabrication of integrated circuit wafers having small critical dimensions.
U.S. Pat. No. 6,277,528 B1 to Tzu et al. describes a method of forming a high transmittance attenuated phase shifting mask blank.
U.S. Pat. No. 5,916,712 to Miyashita et al. describes half tone phase shifting photomasks which have high transmittance for light having a wavelength of 248 nanometers.
U.S. Pat. No. 5,503,951 to Flanders et al. describes an attenuating phase shifting mask having recessed phase shifting and phase shifting regions that is not susceptible to phase defects in the printing regions of the mask.
U.S. Pat. No. 5,786,114 to Hashimoto describes an attenuated phase shift mask with boundary regions formed from the halftone material used to form the circuit pattern regions of the mask. The halftone material in the boundary regions are shielded from a stabilization treatment of the halftone material used to stabilize the transmittance of the halftone material at a higher optimum level.